A magnetostrictive torque sensor has been conventionally used for detecting a torque applying on a component of equipment. A known configuration example of a magnetostrictive torque sensor includes: a columnar substrate having an outer peripheral surface on which a pair of magnetostrictive portions is provided; and a pair of coils that generates a magnetic flux passing through the pair of magnetostrictive portions. In the magnetostrictive torque sensor having such a configuration, when a force in a rotation direction is applied to the substrate, a tensile stress occurs in one of the pair of magnetostrictive portions, and a compressive stress occurs in the other magnetostrictive portion. Accordingly, magnetic permeabilities of the pair of magnetostrictive portions change. The force applying on the substrate is detected by detecting changes of magnetic permeabilities of the pair of magnetostrictive portions.
An amorphous alloy can be used as the magnetostrictive portions, for example. Patent Document 1, for example, discloses: a torque detector including a columnar or tubular torque transfer unit having an outer peripheral surface on which a magnetostrictive effect portion is formed; and a pair of coils. In the torque detector disclosed in Patent Document 1, amorphous alloy foil is attached as the magnetostrictive effect portion to the outer peripheral surface of the torque transfer unit.